Compact Fluorescent Lamps or CFL, commonly referred to as “energy saving” lamps, are energy efficient, consuming up to five times less energy than the conventional incandescent lamps.
For only a few decades ago, light-dimming was only common for incandescent lamps and consisted of switching the current on and off 120 times per second using a solid-state light dimmer, thereby saving energy and allowing the dimmer to be installed in a standard electrical wall-box.
Nowadays, several CFL lamps can also be dimmable, either by means of the same kind of solid-state light dimmer or by means of a so-called step dimmer. The step dimmer is a dimming feature for a CFL lamp where a finite number of dimming states, usually four, can be chosen by means of a certain mains switch ON/OFF sequence.
The present demand from the CFL market is to have a CFL lamp that would be able to function both with step-dimming and linear phase-cut dimming, thus making it much easier to replace any incandescent lamp by such a dimmable CFL lamp. However, the problem is to be able to distinguish between the supply of a “normal” AC mains voltage, namely a voltage having a sinusoidal waveform without phase-cut, and an AC mains voltage through a forward or reverse phase-cut dimmer, namely a phase-cut waveform, thereby making it possible to switch over from a certain fixed dimmed or maximum control value into a continuous dimmer control action, respectively.